This invention concerns packaging and is particularly concerned with packaging for relatively heavy but fragile articles.
Packaging of relatively heavy but fragile articles, such as plaster of paris models and figures, currently involves use of foam rubber and other materials to cushion articles and/or specially shaped polyurethane foam formers. The former are not entirely satisfactory for a heavy article as they do not prevent an article from moving around inside a box or carton. The latter do prevent movement of an article but are relatively expensive to produce and can only be used for the one article.
An object of this invention is to provide packaging for an article, whereby the article can be transported safely, which packaging may be reusable.
According to this invention there is provided packaging for an article to be transported comprising at least one air permeable bag containing particles, especially beads, of a light but relatively rigid material, such as blown or expanded polymer beads, especially polystyrene.
The air permeable bag is preferably made of a plastic material that is microporous. Preferred plastic materials for the bags are of relatively high tear strength, such as polyethylene or polypropylene. The plastic material used for the bags is preferably also an antistatic plastic material. Microporosity may be achieved by perforating or punctuating the plastics material prior to forming a bag or during production and filling of a bag.
For the sake of appearance, the plastic bags are preferably painted or coated with an opaque pigmented finish to give the appearance of satin.
The bags used in the invention will preferably be formed by heat sealing along edges of the overlaid plastic material to form an open ended bag which is then filled with the particles prior to complete edge sealing. Two separate sheets or one folded sheet of plastic material may be used for that purpose. The bags may also be formed from a tubular plastic material cut into suitable lengths, sealed at one end prior to filling and sealed at the other end after filling.
The bags used in the invention may alternatively be of a textile material, such as satin or nylon, and produced by sewing textile pieces together at overlaid edges thereof.
The particles used in the bags of the invention are preferably of different sizes to enable closer packing thereof when air is evacuated from the enclosing bag. Preferably particles in the size range 3-5 millimeters are used for the filling. The preferred particles or beads have a high compressive strength.
The amount of filling in a bag will preferably be chosen so that the bag is sufficiently flexible to allow it to be fitted around an object but also so that air evacuation on compression will produce a generally rigid body, as air is forced out of the bag.
In use, an object to be packaged will be surrounded in a container, such as a cardboard carton or box, by one or more bags of the invention. The weight of the object and pressure exerted on the bags by closing of the container lid will cause air to be evacuated through the microporous walls of the bag. The particles within the bags are thus forced together to form a substantially rigid body molded to the shape of the object being packaged. The bags then do not permit much, if any, movement of the object within the container but the particles themselves are generally able to absorb shocks and point loadings.
Once the container is opened, pressure is released and air can return to the bags, so that they become flexible again. Provided the bags have not been damaged they can be re-used.